function code_draw() {
    var canvas_width = $('#canvas').width();
    var canvas_height = $('#canvas').height();
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    canvas.width = canvas_width;
    canvas.height = canvas_height;
    var sCode = "A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0";
    var aCode = sCode.split(",");
    var aLength = aCode.length;
    var value = [];
    for (var i = 0; i <= 3; i++) {
        var j = Math.floor(Math.random() * aLength);
        var deg = Math.random() * 30 * Math.PI / 180;
        var txt = aCode[j];
        value[i] = txt.toLowerCase();
        var x = 10 + i * 20;
        var y = 20 + Math.random() * 8;
        context.font = "bold 23px 寰蒋闆呴粦";
        context.translate(x, y);
        context.rotate(deg);
        context.fillStyle = code_randomColor();
        context.fillText(txt, 0, 0);
        context.rotate(-deg);
        context.translate(-x, -y);
    }
    value = value.join("");
    $('#canvas').attr('data-code', value)
    for (var i = 0; i <= 5; i++) {
        context.strokeStyle = code_randomColor();
        context.beginPath();
        context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height);
        context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height);
        context.stroke();
    }
    for (var i = 0; i <= 30; i++) {
        context.strokeStyle = code_randomColor();
        context.beginPath();
        var x = Math.random() * canvas_width;
        var y = Math.random() * canvas_height;
        context.moveTo(x, y);
        context.lineTo(x + 1, y + 1);
        context.stroke();
    }
}

function code_randomColor() {
    var r = Math.floor(Math.random() * 256);
    var g = Math.floor(Math.random() * 256);
    var b = Math.floor(Math.random() * 256);
    return "rgb(" + r + "," + g + "," + b + ")";
}

$(function() {
    code_draw();
    $("#canvas").on('click', function() {
        code_draw();
    })
})